Overview - ISO/IEC 21122-1:2022 (JPEG XS Core Coding System)
ISO/IEC 21122-1:2022 specifies the core coding system of JPEG XS - a low-latency, lightweight image coding standard for continuous‑tone grey-scale and colour images. The document defines a codestream syntax and a decompression (decoding) process that enable visually lossless compression at typical compression ratios of 2:1 to 6:1 (and higher depending on image content). The standard is aimed at implementations that minimize end‑to‑end latency to a fraction of a frame, while providing guidance for encoding. Note: channel buffer models to guarantee latency are outside its scope.
Key topics and technical requirements
- Codestream syntax and structure - formal layout of packets, precincts, packets, bitplanes and filler/padding for interoperable compressed data.
- Decoding processes - mandatory procedures to convert codestreams into reconstructed image samples (decoder requirements and conformance language).
- Encoding guidance - recommended steps for producing compressed image data that conform to the codestream syntax.
- Wavelet-based transform - discrete wavelet decomposition and inverse transform definitions used in the core coding pipeline.
- Quantization and inverse quantization - quantizer types (including deadzone quantizers) and reconstruction of coefficients.
- Entropy coding/decoding - lossless encoding stage for quantization indices and sign information.
- Multi-component transformations - tools for colour/component transforms (including reversible transforms for lossless coding).
- Support features (second edition) - added tools for colour filter array (CFA) images, lossless coding up to 12 bits per sample, and 4:2:0 sampling support.
- Terms & definitions, conformance rules - exhaustive normative annexes covering syntax, data structures, entropy decoding, quantization and transforms.
Practical applications and target users
- Real-time video and streaming - low-latency encoding for live contribution, remote production and streaming where minimal delay is critical.
- Broadcast and professional video - visually lossless, lightweight compression for studio links, monitoring and mezzanine transport.
- Camera and sensor vendors - on-camera compression for high-quality output with limited compute and power budget.
- Hardware and FPGA/ASIC implementers - designs that require deterministic, low-latency decoding and simple encoder complexity.
- AR/VR, automotive and IP-based video systems - scenarios requiring high visual fidelity with constrained bandwidth and latency.
Users include codec implementers, product architects, system integrators and standards specialists.
Related standards
- Part of the ISO/IEC 21122 (JPEG XS) series developed by ISO/IEC JTC 1/SC 29. Implementers should consult other parts of the series for profiles, transport bindings and application-specific extensions.
- The standard notes potential patent claims; consult ISO/IEC patent declarations for licensing information.